Visual C++ 2011-5-20

 

一.LockFile和UnlockFile

锁定文件部分区域，防止其他程序进行该部分区域的读写

#include <windows.h>
#include <stdio.h>

void main()
{
    HANDLE hFile;
    HANDLE hAppend;
    DWORD  dwBytesRead, dwBytesWritten, dwPos;
    BYTE   buff[4096];

    // Open the existing file.

    hFile = CreateFile(TEXT("one.txt"), // open One.txt
              GENERIC_READ,             // open for reading
              0,                        // do not share
              NULL,                     // no security
              OPEN_EXISTING,            // existing file only
              FILE_ATTRIBUTE_NORMAL,    // normal file
              NULL);                    // no attr. template

    if (hFile == INVALID_HANDLE_VALUE)
    {
       printf("Could not open One.txt."); 
       return;
    }

    // Open the existing file, or if the file does not exist,
    // create a new file.

    hAppend = CreateFile(TEXT("two.txt"), // open Two.txt
                FILE_APPEND_DATA,         // open for writing
                FILE_SHARE_READ,          // allow multiple readers
                NULL,                     // no security
                OPEN_ALWAYS,              // open or create
                FILE_ATTRIBUTE_NORMAL,    // normal file
                NULL);                    // no attr. template

    if (hAppend == INVALID_HANDLE_VALUE)
    {
       printf("Could not open Two.txt."); 
       return;
    }

    // Append the first file to the end of the second file.
    // Lock the second file to prevent another process from
    // accessing it while writing to it. Unlock the
    // file when writing is complete.

    while (ReadFile(hFile, buff, sizeof(buff), &dwBytesRead, NULL)
            && dwBytesRead > 0)
      {
        dwPos = SetFilePointer(hAppend, 0, NULL, FILE_END);
        LockFile(hAppend, dwPos, 0, dwBytesRead, 0);
        WriteFile(hAppend, buff, dwBytesRead, &dwBytesWritten, NULL);
        UnlockFile(hAppend, dwPos, 0, dwBytesRead, 0);
      }

    // Close both files.

    CloseHandle(hFile);
    CloseHandle(hAppend);
}

二.GetOverlappedResult

此函数可以查询I/O处理过程中的传输状态.如下代码示例,可以通过以下方式查看状态,见SDK示例(Testing for the End of a File)

// Check the result of the asynchronous read
// without waiting (forth parameter FALSE). 
bResult = GetOverlappedResult(hFile,
                              &stOverlapped,
                              &dwBytesRead,
                              FALSE) ; 
     
if (bResult) 
{ 
    float floatOffset=(float)stOverlapped.Offset;
    printf("ReadFile operation completed (%f)\n",floatOffset/dwFileSize);
    // Manual-reset event should be reset since it is now signaled.
    ResetEvent(stOverlapped.hEvent);
} 

三.Dialog消息循环

Dialog有着自己的消息循环,见下示例代码,About消息循环在DialogBox函数中创建

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    int wmId, wmEvent;
    PAINTSTRUCT ps;
    HDC hdc;

    switch (message)
    {
    case WM_COMMAND:
        wmId    = LOWORD(wParam);
        wmEvent = HIWORD(wParam);
        // Parse the menu selections:
        switch (wmId)
        {
        case IDM_ABOUT:
            DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
            break;
        case IDM_EXIT:
            DestroyWindow(hWnd);
            break;
        default:
            return DefWindowProc(hWnd, message, wParam, lParam);
        }
        break;
    case WM_PAINT:
        hdc = BeginPaint(hWnd, &ps);
        // TODO: Add any drawing code here...
        EndPaint(hWnd, &ps);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

// Message handler for about box.
INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
    UNREFERENCED_PARAMETER(lParam);
    switch (message)
    {
    case WM_INITDIALOG:
        return (INT_PTR)TRUE;

    case WM_COMMAND:
        if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
        {
            EndDialog(hDlg, LOWORD(wParam));
            return (INT_PTR)TRUE;
        }
        break;
    }
    return (INT_PTR)FALSE;
}

四.对话框参数

DialogBoxParam 方法多了一个参数,可以在WM_INITDIALOG消息中传递一个参数,同理CreateDialog和CreateDialogParam也是如此

五.ATL窗体类介绍

很好的一篇文章
http://msdn.microsoft.com/en-us/library/aa260759(VS.60).aspx

http://www.vckbase.com/document/viewdoc/?id=1119